THE DIGESTIVE CANAL AS A WHOLE. 
221 
six diverticula arising from the stomach, and twelve longitudinal folds 
in each diverticulum. There are twelve (twice six) gastroileal folds, ar- 
ranged in twos, each pair appearing as the double anterior termination 
of one of the six ileal folds, which, changing their character, extend 
backwards through the colon ; finally, in the rectum there are six rectal 
glands. 
The three divisions of the digestive canal are perfectly natural; their 
existence of itself suggests that they represent the three segments which 
are usually distinguished upon embryological grounds, namely, the fore- 
gut, midgut, Mndgut ( Vorderdarm, Mitteldarm, and Hinterdarm). This 
supposition is strengthened by Bobretzky's 319 observation that in dec- 
apods the embryological foregut forms the oesophagus and Kaumagen, 
while the midgut forms the follicular stomach and diverticula (liver). 
This is a strong confirmation of the conclusion that I have been induced 
to consider probable upon purely anatomical grounds. It seems to me, 
moreover, that Hatschek's 320 observations also point to the same conclu- 
sion, viz, that the ventriculus (Chylusmagen), together with its append- 
ages, represents the midgut, all in front being foregut, and all posterior 
to it arising from the hindgut. 
The principal respects in which the middle division differs from the 
other two is by, 1, its glandular character; 2, the presence of a delicate 
cuticula, probably not chitinous ; and, 3, of unstriated muscles. It seems 
to me now a legitimate problem in insect anatomy to determine whether 
these characteristics are applicable to the midgut of all insects. 
In all parts of the digestive tract the succession of the layers is the 
same: 1st, a cuticula; 2d, an epithelium ; 3d, connective tissue; 4th, 
muscles. Besides which there is stated to be a pavement epithelium 
(serosa) outside the muscles in some insects. This I have not observed 
in the grasshoppers, though it may be present. 
Of the physiological functions of the single parts of the digestive 
canal little is really known, though some observations have been pub- 
lished by Sirodot and Plateaux. 
I should like to interpolate here a comparison, which is curious and 
odd rather than of scientific value. After Malpighi had shown that the 
grasshopper had several stomachs, some of the older authors, according 
to Colin, considered these insects to be ruminants, comparing the vari- 
ous parts of their digestive canal with the divisions of the stomach in 
the true ruminants. Of course this idea is now entirely rejected, but it 
is nevertheless curious to notice that with our present knowledge we 
can trace an analogy between the crop and the rumen, the ventricle of 
the grasshopper and the sheep, while the diverticula with their leaf -bike 
folds singularly imitate the structure of the psalter. Those who are not 
familiar with the anatomy of ruminants, will find a clear and excellent 
account in Huxley's Anatomy of Vertebrated Animals. 
319 Bobretzky : Zur Embryologie der Arthropoden (in Russian) as abstracted by Hoyer in Hoffmann nnd 
Schwalbe. Jahresbericbt der Physiol, u. Anat. fur 1873, p. 314. 
3X1 B. HaUchek: Beitrage zur Entro. Lepidopteren. Jena Zeitschr. Bd. XI. (1877), (p. 17 des Separatab- 
druckes.) 
